1. Field of the Invention
The present invention relates to a method of accurately executing read access of a recording medium having a high recording density while keeping compatibility with a recording medium having a low recording density and a magnetic recording/reproducing apparatus therefor.
2. Related Art of the Invention
In a conventional magnetic recording/reproducing apparatus, e.g., a floppy disk apparatus, a magnetic head 202 shown in, e.g., FIG. 1A is used. The magnetic head 202 is of a laminate tunnel erase type. Erase head structures 214 and 216 are fixed to two sides of a read/write (R/W) head structure 212, and sliders 218 and 220 are fixed to two sides of the resultant assembly. The R/W head is formed by cores 1, 2, and 3 each of which is made of a magnetic material having a relatively large coercive force, and an R/W coil wound around a bobbin. The length of an R/W gap GL is relatively large, and, hence, a floppy disk as a recording medium is magnetized up to a deep portion thereof, as shown in FIG. 1B. The erase head structure is the same as the R/W head structure.
Since the magnetic material having a large coercive force is used as a conventional head material, large residual magnetization is present in the R/W head after write access is executed. For this reason, if a seek operation is performed after the write access, data already recorded on another track is erased or rewritten by the residual magnetization. In the conventional recording/reproducing apparatus, in order to erase the residual magnetization of the head after execution of the write access, a degaussing circuit is normally used.
Along with advances in technologies, a new magnetic material for a head has been developed. The new magnetic material has good high-frequency permeability characteristics and large saturated magnetization but has a small coercive force. As a result, residual magnetization in the head is small even after write access is executed. Thus, the above problem can be eliminated, and the degaussing circuit can be omitted.
With the development of the new magnetic material, the recording density of a recording material, e.g., floppy disk is increased. Various methods for increasing a recording density are known. Of these methods, a method of increasing a line recording density is known. For this purpose, the length of a read/write (R/W) gap must be decreased and a recording frequency must be increased. In recent years, the length of the R/W gap tends to decrease, and disks having a higher recording density gain their popularity on the market.
A conventional recording/reproducing apparatus for a recording medium having a high recording density is arranged as shown in FIG. 2. In order to write data on a recording medium, e.g., a floppy disk, a floppy disk controller (FDC) 115 generates a write gate signal WG and a write data signal WD. The FDC 115 supplies the signal WG to a buffer 116 and a write driver 113, and supplies the signal WD to the buffer 116. The buffer 116 gates the signal WD with the signal WG to generate a signal W, and outputs the signal W to the driver 113. The write driver 113 outputs a current from a power supplier 112 to a switch circuit 130 in accordance with the signals WG and W. The switch circuit 130 supplies a write current from the write driver 113 to a magnetic (R/W) head 110 in accordance with a read/write mode control signal RWM from the FDC 115. Thus, the data can be written on a floppy disk 140.
When data is read out from the floppy disk 140, a signal read out from the disk 140 by the R/W head 110 is wave-shaped by a shaping circuit 132, and the shaped signal is supplied to a digitizer 134. The digitizer 134 converts the signal from the circuit 132 into a digital signal, and outputs the digital signal to the FDC 115 as a signal RD. Thus, data recorded on the floppy disk 140 can be read out.
The recording medium is accessed as described above. When the length of the R/W gap is decreased, the depth of magnetization in the recording medium is decreased as compared to that obtained when the conventional R/W head is used, as shown in FIG. 1C. Since a recording frequency is often different, it is difficult to provide compatibility, and a problem in terms of cost is also posed. A strong demand has arisen for a magnetic recording/reproducing apparatus having compatibility with recording media having different recording densities.
As described above, as a recording density is increased, the depth of magnetization in the recording medium is decreased as compared to that obtained when the conventional R/W head is used. In addition, an output voltage appearing across the R/W coil of the R/W head tends to decrease. For this reason, the influence of noise is not negligible, and a phenomenon that is not known in a conventional apparatus tends to occur. For example, a read error sometimes occurs.